Printed circuit boards consist of an insulating basic material, generally plastic, are provided with printed conductors and are assembled with electronic components by soldering with the printed conductors. They are tested once or several times, e.g. once as a bare printed circuit board and later once again after assembly is completed. For this, they are contacted in a test device with needles at specific contact points among which specific electrical parameters—such as e.g. continuity—are tested via contacting needles and measuring instruments connected thereto. A printed circuit board of the usual design can have several hundred contact points which must be contacted in different combinations for measurement.
The contact points may be places on printed conductors, soldering points or even places on electronic components, such as e.g. legs of ICs.
Since contact points on printed conductors are usually arranged in a specified dot matrix, test devices are known with a needle plate having needles on all matrix dots. This allows very fast contacting of all matrix dots, inter alia also of the desired contact points. However, such test devices are extremely elaborate since they have a multiplicity of needles, only a few of which are being used for a test procedure.
Furthermore, test devices with few needles are known which are moved during the testing from one contact point to the next. Such test devices are also very elaborate in terms of their design and especially slow because of their low needle speed.
Generic test devices of the type indicated in the preamble of claim 1 feature only as many needles on a needle plate as are required for testing a specific printed circuit board. They are thus more economical than devices which bear needles on all matrix dots. Here, the needles are arranged in the pattern of the contact points so that they meet the contact points upon movement of the needle plate against the printed circuit board. A test procedure with a simultaneous contacting of all contact points requires only one single lift of the needle plate so that testing can be done very fast with these test devices.
A major disadvantage of known generic test devices is, however, that when testing different printed circuit boards, a separate needle plate with the corresponding needle pattern must be kept available for each type of printed circuit board to be tested. This requires major investment expenditures. With a small series of printed circuit boards, it must be carefully considered whether it is worthwhile to manufacture and provide a corresponding needle plate.